Partially Sulfurized Nickel-Cobalt LDH on CNT-coated Aramid Fiber for High-performance Yarn-shaped Supercapacitors

Abstract

Layered double hydroxides (LDHs) have been considered as highly promising materials for supercapacitors. However, the poor electronic conductivity and limited active sites of LDH materials restricts the further applications in supercapacitors. To overcome these limitations, this study develops the sulfurization of nickel-cobalt LDH (NiCo-LDH) on aramid yarn for flexible supercapacitors. NiCo-LDH was loaded onto the carbon nanotube-coated aramid yarn via coprecipitation strategy. Subsequent sulfurization partially converted the LDH into bimetallic sulfide (CoNi2S4), resulting in a hybrid electrode (NiCo-LDH-S) with superior electrochemical performance. In the three-electrode system, the NiCo-LDH-S exhibit the areal capacitance of 9818.48 mF cm-2 (current density of 5 mA cm-2). This electrode material was subsequently assembled into a parallel-symmetric supercapacitor. Structural characterization and electrochemical testing revealed the device exhibits outstanding areal capacitance (526.64 mF cm-2) and energy density (151.67 μWh cm-2) at a current density of 0.5 mA cm-2, alongside remarkable cycling stability. After 10,000 charge-discharge cycles, the capacitance retention rate reached 86.05%. The enhanced performance mainly benefits from enhanced conductivity and enriched active sites through sulfurization treatment. Our work offers new insights for high-performance flexible energy storage devices, being highly significant in wearable electronics.